Chapter 4
Evolution and
Biodiversity
Core Case Study
Earth: The Just-Right, Adaptable
Planet
During the 3.7 billion
years since life arose,
the average surface
temperature of the
earth has remained
within the range of 1020oC.
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Figure
ORIGINS OF LIFE
1 billion years of chemical change to form the
first cells, followed by about 3.7 billion years of
biological change.
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Figure
Biological
Evolution
This has led to
the variety of
species we find
on the earth
today.
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Figure
How Do We Know Which Organisms
Lived in the Past?
Figure
EVOLUTION, NATURAL
SELECTION, AND ADAPTATION
Biological evolution by natural selection
involves the change in a population’s genetic
makeup through successive generations.
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genetic variability
Mutations: random changes in the structure or
number of DNA molecules in a cell that can be
inherited by offspring.
Natural Selection and Adaptation:
Leaving More Offspring With
Beneficial Traits
Three conditions are necessary for biological
evolution:
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Genetic variability, traits must be heritable, trait
must lead to differential reproduction.
An adaptive trait is any heritable trait that
enables an organism to survive through natural
selection and reproduce better under prevailing
environmental conditions.
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Coevolution: A Biological Arms Race
Interacting species can engage in a back and
forth genetic contest in which each gains a
temporary genetic advantage over the other.
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This often happens between predators and prey
species.
Hybridization and Gene Swapping:
other Ways to Exchange Genes
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New species can arise through hybridization.
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Occurs when individuals to two distinct species
crossbreed to produce an fertile offspring.
Some species (mostly microorganisms) can
exchange genes without sexual reproduction.
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Horizontal gene transfer
Limits on Adaptation through
Natural Selection
A population’s ability to adapt to new
environmental conditions through natural
selection is limited by its gene pool and how
fast it can reproduce.
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Humans have a relatively slow generation time
(decades) and output (# of young) versus some
other species.
Common Myths about Evolution
through Natural Selection
Evolution through natural selection is about
the most descendants.
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Organisms do not develop certain traits because
they need them.
There is no such thing as genetic perfection.
GEOLOGIC PROCESSES, CLIMATE
CHANGE, CATASTROPHES, AND
EVOLUTION
The movement of solid (tectonic) plates
making up the earth’s surface, volcanic
eruptions, and earthquakes can wipe out
existing species and help form new ones.
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The locations of continents and oceanic basins
influence climate.
The movement of continents have allowed
species to move.
225 million years ago
225 million years ago
65 million years ago
135 million years ago
Present
Fig. 4-5, p.
Climate Change and Natural
Selection
Changes in climate throughout the earth’s
history have shifted where plants and animals
can live.
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Figure
Catastrophes and Natural Selection
Asteroids and meteorites hitting the earth and
upheavals of the earth from geologic processes
have wiped out large numbers of species and
created evolutionary opportunities by natural
selection of new species.
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ECOLOGICAL NICHES AND
ADAPTATION
Each species in an ecosystem has a specific
role or way of life.
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Fundamental niche: the full potential range of
physical, chemical, and biological conditions and
resources a species could theoretically use.
Realized niche: to survive and avoid
competition, a species usually occupies only part
of its fundamental niche.
Generalist and Specialist Species:
Broad and Narrow Niches
Generalist
species tolerate a
wide range of
conditions.
●Specialist
species can only
tolerate a narrow
range of
conditions.
●
Figure
SPOTLIGHT
Cockroaches: Nature’s Ultimate
Survivors
Figure
Specialized Feeding Niches
Resource partitioning reduces competition
and allows sharing of limited resources.
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Figure
Evolutionary Divergence
Each species has a
beak specialized to
take advantage of
certain types of food
resource.
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Figure
SPECIATION, EXTINCTION, AND
BIODIVERSITY
Speciation: A new species can arise when
member of a population become isolated for a
long period of time.
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Genetic makeup changes, preventing them from
producing fertile offspring with the original
population if reunited.
Geographic Isolation
…can lead to reproductive isolation,
divergence of gene pools and speciation.
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Figure
Extinction: Lights Out
Extinction occurs
when the
population cannot
adapt to changing
environmental
conditions.
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The golden toad of Costa Rica’s
Monteverde cloud forest has
become extinct because of
changes in climate.
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Figure
Cenozoic
Era
Period
Quaternary
Millions of
years ago
Today
Bar width represents relative
number of living species
Extinction
Tertiary
65
Extinction
Mesozoic
180
Extinction
Permian
Carboniferous
Paleozoic
345
Extinction
Triassic: 35% of animal families,
including many reptiles and marine
mollusks.
Permian: 90% of animal families,
including over 95% of marine
species; many trees, amphibians,
most bryozoans and brachiopods,
all trilobites.
Devonian: 30% of animal
families, including agnathan and
placoderm fishes and many
trilobites.
Devonian
Silurian
Ordovician
Cambrian
by human activities. Many species are
expected to become extinct within the next
50–100 years.
Extinction
Triassic
250
Current extinction crisis caused
Cretaceous: up to 80% of ruling
reptiles (dinosaurs); many marine
species including many
foraminiferans and mollusks.
Cretaceous
Jurassic
Species and families
Fig. 4-12, p. 93
experiencing
mass extinction
500
Extinction
Ordovician: 50% of animal
families, including many
trilobites.
Fig. 4-12, p.
Effects of Humans on Biodiversity
The scientific consensus is that human
activities are decreasing the earth’s
biodiversity.
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Figure
GENETIC ENGINEERING AND THE
FUTURE OF EVOLUTION
We have used artificial selection to change
the genetic characteristics of populations with
similar genes through selective breeding.
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We have used
genetic engineering
to transfer genes from
one species to another.
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Figure
Genetic Engineering:
Genetically Modified Organisms (GMO)
GMOs use
recombinant DNA
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genes or portions
of genes from
different
organisms.
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Figure
How Would You Vote?
To conduct an instant in-class survey using a classroom response
system, access “JoinIn Clicker Content” from the PowerLecture main menu
for Living In the Environment.
Should we legalize the production of human
clones if a reasonably safe technology for
doing so becomes available?
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a. No. Human cloning will lead to widespread
human rights abuses and further overpopulation.
b. Yes. People would benefit with longer and
healthier lives.
THE FUTURE OF EVOLUTION
Biologists are learning to rebuild organisms
from their cell components and to clone
organisms.
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Cloning has lead to high miscarriage rates, rapid
aging, organ defects.
Genetic engineering can help improve human
condition, but results are not always
predictable.
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Do not know where the new gene will be located
in the DNA molecule’s structure and how that will
affect the organism.
Controversy Over
Genetic Engineering
There are a number of privacy, ethical, legal
and environmental issues.
●Should genetic engineering and development
be regulated?
●What are the long-term environmental
consequences?
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Case Study:
How Did We Become Such a Powerful
Species so Quickly?
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We lack:
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strength, speed, agility.
weapons (claws, fangs), protection (shell).
poor hearing and vision.
We have thrived as a species because of our:
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opposable thumbs, ability to walk upright,
complex brains (problem solving).